3-amino-5-benzyl-1,2,4-oxadiazoles

ABSTRACT

3-Amino-5-benzyl-1,2,4-oxadiazole and related compounds substituted on the Alpha -carbon atom and/or on the phenyl ring are useful as antiinflammatory agents.

nited States Patent H9] Hummer et al.

[ 3-AMlNO-5-BENZYL-l,2,4-

OXADIAZOLES [75] Inventors: Hermann Breuer, Burgweinting; Ernst Schulze, Regensburg, both of [21] Appl. No.: 55,253

[52] U.S. Cl. ..260/307 G, 260/558 R, 260/559 R,

424/272 [51] Int. Cl. ..C07d 85/52 [58] Field of Search ..260/307 G [56] References Cited UNITEDSTATES. PATENTS 3,564,606 2/1971 Breuer ..260/307 mlMarch 13, I973 OTHER PUBLICATIONS Burger, Medicinal Chemistry" Third Edition, Part ll, Wiley-Interscience; page 964; 1970 Adams et al., C. A. 48, 8223i (1954) Eloy et al., C. A. 71, 49862n (1969) Primary Examiner-Alex Mazel Assistant ExaminerR. V. Rush Attorney-Lawrence S. Levinson, Merle J. Smith and Donald J. Perrella [57] ABSTRACT 3-Amino-5-benzyl-l,2,4-oxadiazole and related compounds substituted on the a-carbon atom and/or on the phenyl ring are useful as antiinflammatory agents.

11 Claims, No Drawings 3-AMINO-5-BENZYL-l ,2,4-OXADIAZOLES SUMMARY OF THE INVENTION This invention relates to new unsubstituted and substituted S-amino-S-benzyl-l,2,4oxadiazoles of the formula R2 ll N wherein R is hydrogen, halogen, lower alkyl or lower alkoxy; R is hydrogen, lower alkyl, cyclo-lower alkyl, phenyl, lower alkylphenyl, lower alkoxyphenyl, halophenyl or trifluoromethylphenyl; and R is hydrogen, lower alkyl, phenyl, lower alkylphenyl, lower alkoxyphenyl or halophenyl.

The lower alkyl groups represented by the symbols, themselves or as part of a lower alkylphenyl group, are straight or branched chain hydrocarbon groups of up to seven carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl or the like. The lower alkoxy groups are similar oxygen containing groups, such as methoxy, ethoxy, propoxy, isopropoxy or the like.

The cyclo-lower alkyl groups are three to six carbon cyclo-aliphatic groups including cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. The halogens are the four common halogens, but chlorine and bromine are preferred.

Preferred within the lower alkyl and lower alkoxy groups are those with one to three carbon atoms and I DETAILED DESCRIPTION OF THE INVENTION The compounds of formula I are produced by cyclizing an N-(hydroxyamidino)-2-phenylacetamide, or an acid salt thereof, e.g., a hydrohalide like the hydrochloride, of the formula (11) mm R1 M V NOE oo-NH in the presence of a base, e. g., an alkali metal hydroxide, like sodium hydroxide, potassium hydroxide or the like, in an aqueous medium, preferably at a reduced temperature, e.g., at about 0 to 5 C.

The compounds of formula II may be derived from the unsubstituted or appropriately substituted phenylacetic halide, preferably chloride, of the formula (III) by reaction with cyanamide, for example, by adding the phenylacetic halide to the cyanamide at areduced temperature, e.g., below about 5 C. in alkaline solution.

The R,,R -phenylacetyl halides are produced from the appropriate phenylacetic acid and thionyl chloride. The resulting phenylacetyl cyanamide of the formula is treated with hydroxylamine, or an acid salt thereof, e.g., a hydrohalide like the hydrochloride, in the presence of a hydrogen halide acceptor like pyridine or other base to obtain the compound offormula II.

The new compounds of this invention have anti-inflammatory properties and are useful as anti-inflammatory agents, for example, to reduce local inflammatory conditions such as those of an edematous nature or resulting from proliferation of connective tissue in various mammalian species such as rats, dogs and the like when given orally in dosages of about 5 to 50 mg/kg/day, preferably 5 to 25 mg/kg/day, in single or 2 to 4 divided doses, as indicated by the carageenan edema assay in rats. The active substance may be utilized in compositions such as tablets, capsules, solutions or suspensions containing up to about 300 mg. per unit of dosage of a compound or mixture of compounds of formula I. They may be compounded in conventional manner with a physiologically acceptable vehicle or carrier, excipient, binder, preservative, stabilizer, flavor, etc. as called for by accepted pharmaceutical practice. Topical preparations containing about 0.( )l to 3 percent by weight of active substance in a lotion, salve or cream may also be used.

The following examples are illustrative of the invention. It will be appreciated variously substituted phenylacetyl halides of formula III or their derivatives of formulas II and IV may be used in the same manner as in the following examples to obtain other compounds of this invention in addition to the illustrative members which follow. All temperatures are on the centigrade scale.

EXAMPLE I 5 and permitted to stand at this temperature for several hours. The yield amounts to 56.6 g. of 3-amino- S-benzyl-l ,2,4-oxadiazole, m.p. l l0-l 13.

EXAMPLE 2 3-Amino-5-( l -Phenylpropyl)-l ,2,4-Oxadiazole 258 g. of 2-phenylbutyryl chloride dissolved in 500 ml. of acetone and sodium hydroxide solution are added simultaneously dropwise at a temperature of 0 to 5 to a mixture of 60 g. of cyanamide, 136 ml. of 30 percent sodium hydroxide solution and 1.35 liters of water. The pH is continually controlled so as not to go below 10 to II. The mixture is stirred for 1 hour and the clear solution is then made strongly acid with concentrated hydrochloric acid, while holding the temperature below 5.

The oil which precipitates is taken up in chloroform, separated from water, the chloroform solution is dried with magnesium sulfate and the solvent is then evaporated. 269 g. of crude 2-phenylbutyroyl cyanamide remain, which, without further purification, are dissolved in 860 ml. of ethanol. This solution is added to a solution of 151 g. of hydroxyl-amine hydrochloride in 345 ml. of pyridine. The reaction proceeds exothermically. While cooling externally, care is taken that the temperature does not exceed 40.

The reaction mixture is permitted to stand overnight at room temperature, the solution is then concentrated and treated with sufficient 2N sodium hydroxide solution so that the solution reacts strongly basic. 3-Aminol-phenylpropyl)- l ,2,4-oxadiazole precipitates. The product is recrystallized from about 300 ml. of ethanol to obtain 138 g. melting at 99-l00.

The following additional compounds of formula I are produced according to the procedure of Example 2 by substituting for the Z-phenylbutyryl chloride of that Example the phenyl-acetyl chloride having the same substitutents R R, and R; as those in the final products wherein R is hydrogen, chlorine, bromine, lower alkyl or lower alkoxy; R is hydrogen, lower alkyl, cyclolower alkyl, phenyl, lower alkyl-phenyl or lower alkoxyphenyl; and R is hydrogen, lower alkyl, phenyl, lower alkylphenyl or lower alkoxyphenyl.

2. A compound as in claim 1 wherein R and R each is hydrogen and R is lower alkyl.

3. A compound as in claim 1 wherein R is hydrogen and R and R each is lower alkyl.

4. A compound as in claim 1 wherein R and R each is hydrogen and R is cyclo-lower alkyl.

5. A compound as in claim 1 wherein R is lower alkoxy, R is phenyl or lower alkoxyphenyl and R is hydrogen.

6. A compound as in claim 1 wherein R R and R each is hydrogen.

7. A compound as in claim 2 wherein the lower alkyl group is ethyl.

8. A compound as in claim 2 wherein the lower alkyl group is propyl.

9. A compound as in claim 4 wherein the cyclo-alkyl group is cyclopentyl.

below: 10. A compound as in claim 4 wherein the cyclo- R2 III (I? NH2 I R1 R3 0 M.P., Solvent of Example R1 R2 R3 degrees recrystallization a H G H 156-158 Methanol.

4 H CHzCHzCH II 89-91 n-Heptane.

5 II -CH(CH;)2 II 107-109 Do.

6 r. H H II 108-112 Isopropanol.

7 II II II Ell-J3 Petroleum ether.

8 C1130 ll 133 136 Isopmpanol.

n ..o1n0 oc1n n 149-451 Methanol.

10 CII3O II ll 134-135 Isopropanol.

11 II D Q 218052 Methylene glycol.

What is claimed is: l. A compound of the formula 

1. A compound of the formula
 2. A compound as in claim 1 wherein R1 and R3 each is hydrogen and R2 is lower alkyl.
 3. A compound as in claim 1 wherein R1 is hydrogen and R2 and R3 each is lower alkyl.
 4. A compound as in claim 1 wherein R1 and R3 each is hydrogen and R2 is cyclo-lower alkyl.
 5. A compound as in claim 1 wherein R1 is lower alkoxy, R2 is phenyl or lower alkoxyphenyl and R3 is hydrogen.
 6. A compound as in claim 1 wherein R1, R2 and R3 each is hydrogen.
 7. A compound as in claim 2 wherein the lower alkyl group is ethyl.
 8. A compound as in claim 2 wherein the lower alkyl group is propyl.
 9. A compound as in claim 4 wherein the cyclo-alkyl group is cyclopentyl.
 10. A compound as in claim 4 wherein the cyclo-lower alkyl group is cyclohexyl. 